1. Field of the Invention
This invention generally relates to an imaging method and system using laser beam scanning, and, in particular, to a laser beam scanning system and method for use in various recording machines, such as printers, copiers and facsimile machines.
2. Description of the Prior Art
A typical prior art laser beam scanning system for use in various recording machines is schematically shown in FIG. 27. As shown, the laser beam scanning system for imaging includes a semiconductor laser 201 from which a laser beam 202 modulated with an image signal supplied thereto is emitted. The laser beam thus emitted passes through a collimator lens 23 and cylindrical lens 204 and impinges on a polygon mirror 205 which is provided with a plurality of reflecting facets arranged in the circumferential direction and which rotates at high speed. Thus, the laser beam is deflected by the rotating polygon mirror 205 over a predetermined angle defined by the size of the reflecting facet repetitively. The laser beam reflected by the polygon mirror 205 then passes through a f.theta. lens 206, and after having been reflected by a reflecting mirror 207, the laser beam passes through a cylindrical lens 208 and is focused onto an imaging surface 209, such as a photosensitive surface.
Since the laser beam is deflected over a predetermined angle by the rotation of the polygon mirror 205, the laser beam focused on the imaging surface 209 moves along a scanning line 210. The direction of this scanning line 210 is often called an optical or main scanning direction. The imaging surface 209 is normally caused to move in a direction perpendicular to the scanning line 210 and this direction of movement of the imaging surface 209 is often called an auxiliary scanning direction. The laser beam is passed through the f.theta. lens 206 before being focused on the imaging surface 210 so as to cause the laser beam to move along the scanning line 210 at constant speed linearly.
A sync detecting mirror 211 is normally disposed such that it receives the laser beam which is directed to the start end 210a of the scanning line 210. Thus, the laser beam reflected by the sync detecting mirror 211 is directed to a light-receiving element 213 of a sync detecting device 212, which generates a horizontal sync signal.
Such a laser beam scanning system may be advantageously applied to various imaging machines. However, there are several aspects which still need to be improved for wider applications.